Some optical disk devices are constructed to include a front panel formed with an opening through which a disk tray enters and exits. In such an optical disk device, after an optical disk is placed on the disk tray exiting through the opening, the optical disk together with the disk tray is drawn into a predetermined position inside the device.
In this type of disk device, after the optical disk is drawn and stored in the inside of the device, a turntable moves upwardly from a predetermined lowered position to a predetermined raised position, and the optical disk is placed on the turntable and held between the turntable and a clamper. In this condition, the optical disk is then rotated at a predetermined rpm by the rotation of the turntable.
For example, in a reproducing operation, a recording and reproducing device reproduces a signal recorded on the optical disk. Specifically, the reproduction of a predetermined information signal is carried out by reciprocally moving an optical pickup for signal reading between an outer region and an inner region of the optical disk in accordance with the track position of the signal recorded in a predetermined area of the optical disk.
An optical disk device of the above-mentioned type necessitates a total of four basic operations requiring the driving force of a motor and the like: a disk transport operation for reciprocally moving the disk tray inwardly or outwardly of the device to transport the optical disk inwardly or outwardly of the device; a turntable raising/lowering operation for reciprocally moving the turntable between the predetermined lowered position and the predetermined raised position; a disk rotating operation for rotatably driving the turntable to rotate the optical disk; and a pickup feed operation for reciprocally moving the optical pickup between the outer region and the inner region of the optical disk.
Typically, of the above-mentioned four operations, the disk rotating operation and the pickup feed operation have been performed by respective purpose-built motors, and the disk transport operation and the turntable raising/lowering operation have been performed continuously by a single motor.
On the other hand, there is a prior art optical disk device such that a single motor effects a total of three operation: the above-mentioned disk transport operation, the above-mentioned turntable raising/lowering operation and the above-mentioned pickup feed operation, so that all of the operations including the above-mentioned disk rotating operation are performed by a total of two motors (see, for example, the publication of Japanese Patent Application Laid-Open No. 2000-222803).
In this optical disk device, a power transmission mechanism switching mechanism is operated in response to the operation of moving the optical pickup further inwardly of the data area of the optical disk, to perform switching between a driving mechanism for the pickup feed operation and a driving mechanism for the turntable raising/lowering operation, for transmission of the driving force of the motor.
However, the operation of the power transmission mechanism switching mechanism itself is performed in response to the operation of moving the optical pickup itself further inwardly of the data area of the optical disk in the optical disk device disclosed in the above-mentioned publication. For switching between the pickup feed operation and the turntable raising/lowering operation, it is necessary to move the optical pickup further widely inwardly from the data area of the optical disk. However, a spindle motor for the disk rotating operation is provided near the center of an inner region of the optical disk.
For this reason, it is necessary to provide a space for movement of the optical pickup between the mounting surface of the spindle motor and the rear surface of the turntable to avoid the interference of the optical pickup with an outer peripheral part of the spindle motor during the inward movement of the optical pickup from the data area of the optical disk.
To achieve this, for example, the spindle motor having a protruding rotation shaft as long as about 20 mm from the mounting surface of the spindle motor is used (typically about 8 mm), and the optical pickup itself having a relatively thin structure with a height of less than about 20 mm is adopted.
However, the shaft runout of the rotation shaft increases in proportion to a distance from the mounting surface of the spindle motor to the rear surface (or the disk holding surface) of the turntable (that is, the length of the rotation shaft). As the distance increases, the amount of eccentricity (the runout of the rotation axis) of the optical disk rotating integrally with the turntable accordingly increases. In some instances, there is a danger that no signals can be recorded on the optical disk or reproduced.
Further, the relatively thin optical pickup having a height of about 20 mm, which is required to refract the optical path of a laser with respect to the direction of the impingement of the laser on the optical disk, causes the addition of optical parts to result in increased costs as compared with an optical pickup of a non-refraction type. That is, there has been a problem that it is impossible to use an inexpensive optical pickup so that the device is not constructed at low costs.